CN105356959B - The synchronization of the platform of separation in HD radio broadcasting single frequency networks - Google Patents
The synchronization of the platform of separation in HD radio broadcasting single frequency networks Download PDFInfo
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- CN105356959B CN105356959B CN201510809403.5A CN201510809403A CN105356959B CN 105356959 B CN105356959 B CN 105356959B CN 201510809403 A CN201510809403 A CN 201510809403A CN 105356959 B CN105356959 B CN 105356959B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04H—BROADCAST COMMUNICATION
- H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
- H04H20/65—Arrangements characterised by transmission systems for broadcast
- H04H20/67—Common-wave systems, i.e. using separate transmitters operating on substantially the same frequency
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Abstract
The present invention discloses the synchronization of the platform for the separation being related in HD radio broadcasting single frequency networks.A kind of broadcasting method is provided, including：It is sent using first transmitter including the signal with the multiple data frames synchronous about the first GPS pulse signal, signal is received at the first remote transmitter, frame synchronization is made to be transferred to multiple receivers from remote transmitter in the second GPS pulse signal and by synchronization frame at the first remote transmitter.Additionally provide the system for realizing this method.
Description
The application be application No. is the 201310426204.7, applying date on December 3rd, 2009, it is entitled " HD without
The synchronization of the platform of separation in line electricity Broadcast Single Frequency Network " divisional application (its apply for the first time application No. is
200980153210.1st, the applying date is on December 3rd, 2009, entitled " point in HD radio broadcasting single frequency networks
From platform synchronization ") divisional application.
Technical field
The present invention relates to radio broadcasting systems, more specifically, are related to the such system for including multiple transmitters.
Background technology
iBiquity Digital Corporation HD RadioTMSystem is designed that from current analog amplitude modulation
(AM) it is steadily developed to (IBOC) system on the in-band channel of complete number with frequency modulation (FM) radio.This system is in existing
Frequently in (MF) and superfrequency (VHF) radio band from land transmitter to Mobile portable formula fixed reception device convey digital audio and
Data service.Broadcaster can utilize new higher quality and more strong digital signal simultaneously continuous transmission simulation AM and
FM so that its own and their audience can be digital radio from analog converting, and keep their current frequency simultaneously
Rate is distributed.
The design is by providing three kinds of new type of waveform：Mixing, extended hybrid and digital, to provide to number
The flexible means of broadcast system transition.Mixed type and extended hybrid type remain simulation FM signals, and all digital type is not.Institute
All meet the spectrum emission mask currently distributed there are three types of type of waveform.
Digital signal is modulated using Orthogonal Frequency Division Multiplexing (OFDM).OFDM is a kind of parallel modulation scheme, wherein,
Data flow modulates a large amount of orthogonal sub-carriers of simultaneous transmission.OFDM is intrinsic flexible, easily logic channel is reflected
It is mapped to different subcarrier groups.
The National Radio Systems committee, the standard setting supported by NAB National Association of Broadcasters and consumer electronics association
Tissue, the IBOC standards for being named as NRSC-5A are employed in September, 2005.It is incorporated in the disclosure by reference
NRSC-5A and its update NRSC-5B, elaborate for by AM and FM broadcast channel broadcasts digital audio and auxiliary data
It is required that.The standard and its citation shelves are included for RF/ transmission subsystems and are transmitted detailed with service multiplexing subsystem
Explanation.It can be from the website http of NRSC://www.nrscstandards.org/SG.asp obtains the copy of the standard.
The HD Radio of iBiquityTMTechnology is a kind of realization of NRSC-5IBOC standards.About HD RadioTMTechnology more into one
The information of step can be found in www.hdradio.com and www.ibiquity.com.
Typical HD radio broadcastings are realized is divided into commonly known as exporter by content-aggregated and audio codec
Thing.Exporter will usually handle source and the audio coding of star turn service (MPS), that is, the mirror image in analog channel
Digital audio.Be fed to exporter can be inducting device, which polymerize the cofeature in addition to MPS.Then, it exports
Device generates Radio Broadcast Data packet and those data is forwarded a packet to modem portion or the excitation of driver platform
Device, driver platform are commonly known as exciter engine (exgine).
In some cases, it is desired to HD radio broadcasting systems are embodied as single frequency network (SFN).It is in general, single
Frequency networks or SFN are the radio networks that wherein several transmitters send same signal by same channel simultaneously.Simulate FM
It can be operated in this way with AM radio broadcastings net and digital broadcast networks.A target of SFN is increase overlay area
And/or outage probability is reduced, because total signal strength received can lose and/or cover sternly due to landform in covering
The position increase of weight.
Another target of SFN is to efficiently use radio-frequency spectrum, and different transmission is used from each coverage
Traditional multi-frequency network (MFN) transmission of frequency is compared, enabling provides more radio programs.In multi-frequency network, it is
Government broadcasting business establishes hundreds of station；Therefore, many frequencies have been used.Simultaneous transmission program meeting over multiple frequencies
The audience for usually not remembering retuning their radio when propagating between overlay area is generated to obscure.
A kind of reduced form of SFN can be realized by the co-channel repeater of low-power consumption or booster, repeater or increasing
Strong device is used as gap-filler transmitter.In the U.S., FM boosters and converter are the FM stations of special category, they receive full services
The signal at FM stations, and by those signal transmissions or be re-transmitted to otherwise be also due to landform or other factors will not be from master
Signal receives the region satisfactorily serviced.Initially, FM boosters are the converters in the same frequency of main website.1987
Before year, FM boosters are limited to receive using directly wireless (off-air) by FCC and re-transmission method is (that is, relaying
Device).The change of FCC rules allows the full service station of their relays using substantially any method of communicating signals and until 20%
Maximum allowable Effective Radiated Power power stage.By this rule variation, FM boosters are substantially the son of SFN now
Class.Region is filled or extended in many home broadcasting companies currently using FM boosters, particularly such as San Francisco it
The mountainous region of class.
In the overlay area of overlapping, SFN transmits the precise forms that can be considered as multipath propagation.Radio receiver connects
Receive multiple echoes of same signal, the structural or destructive interference (also referred to as self-interference) between these echoes may be led
Cause decline.This is problematic, because decline is frequency-selecting (rather than flat decline), because the time dispersion of echo may be led
Cause intersymbol interference (ISI).
When receiver is located in the range of more than one transmitter, good acceptance criteria include relative signal intensity and
Total transmission delay.The relationship of two or more transmission signals of location expression of the relative signal intensity based on receiver, and
Total transmission delay be calculate slave signal leave studio position at the time of to it reach receiver at the time of disappearance
Time interval.This delay can the signal path based on specific studio transmitter link between different transmitters
It is different.
In the SFN of HD radio systems is realized, an exporter can be applied in combination with many exciter engines, to change
Into covering.Inventor has been observed that wanting for the operation to meeting the single frequency network in the following radio broadcasting system for HD
The needs for the system and method asked.
For the system based on OFDM of such as HD radio broadcasting systems etc, it is not complete one that transmitter, which must radiate,
Sample but identical play signal.In this way, the frequency and phase of subcarrier must be radiated as very high tolerance.Ofdm system
In carrier wave between any frequency shift (FS) result in intersymbol interference and the Doppler frequency shift felt in a frequency domain.For
HD radio systems, frequency shift (FS) are estimated in~20Hz.In addition, individually sub-carrier frequencies must occur simultaneously.Each
Transmitter must all radiate identical OFDM symbol in same time, so that data are synchronous in the time domain.This synchronization exists
Guard time interval is heavily dependent on, the maximum delay which can tolerate based on ofdm system
Or echo.It has an effect on the maximum distance between transmitter.OFDM receiver is periodically to receiving in scheduled time span
Signal sampled.Between these sampling times (in guard time interim), receiver ignores any receive
Frequency.For HD radio broadcasting systems, in the necessary time alignment to 75 μ sec of each OFDM symbol, to make FM systems
Correctly operate.Preferably, it is aligned in 10 μ sec.
Another requirement is that independent subcarrier must carry each symbol identical data.In other words, it comes from
The subcarrier of different transmitters must be " position is accurate ".It means that for each node in SFN, from exporter
The digital information received at transmitting position must include identical position (that is, MPS digital audio, program service data
(PSD), it stands information service (SIS) and advanced application service (AAS) or other data all must be identical).In addition, letter
Breath must also in an identical manner be handled by each exciter engine so that for each transmission node of network, output
Waveform is identical.
It is also expected to the various equipment asynchronous operations of network are formed, it is entire without requiring so that equipment can reach the standard grade or offline
Network is reset.It must be in independent node reboot (i.e., it is possible to make each in SFN independently of all other node
Node is offline and reach the standard grade, without influencing system performance) during keep timing accuracy as described above and " position accuracy ".
Each node of SFN, which must also have, adjusts transmission delay to solve the ability that propagation delay can simultaneously tune SFN.
Invention content
In a first aspect, the present invention provides a kind of broadcasting method, including：It is sent using first transmitter including with
The signal for multiple data frames that one GPS pulse signal synchronizes receives signal, in the first remote transmission at the first remote transmitter
At device multiple receivers are transferred to from remote transmitter by frame synchronization in the second GPS pulse signal and by synchronization frame.Also provide
The system for realizing this method.
On the other hand, the present invention provides a kind of broadcast system, including：First transmitter includes and for sending
The signal for multiple data frames that one GPS pulse signal synchronizes；And first remote transmitter, including being used to make frame synchronization in second
GPS pulse signal is simultaneously used for sync frame transmission to the circuit of multiple receivers.
On the other hand, the present invention provides the method that the platform made in broadcast system synchronizes, including：In base transmitter and
Master clock signal, the predetermined time interval before the first clock pulses in master clock signal are received at multiple remote transmitters
Inherent Ji Fasheqichu starts audio sample, and audio sample is combined as audio frame, and what is occurred after the first clock pulses is exhausted
To the 1 frame number time of layer, start audio frame being transferred to remote transmitter from base transmitter, audio is received at remote transmitter
Frame and since corresponding to the time of the audio frame of absolute 1 frame number time of layer transmits audio frame from remote transmitter.
Description of the drawings
Fig. 1 is the diagram of single frequency network.
Fig. 2 is the block diagram of single frequency network.
Fig. 3 is the block diagram of radio broadcasting system.
Fig. 4 is the block diagram of certain parts of exporter and exciter engine/driver.
Fig. 5 is another block diagram of certain parts of exporter and exciter engine/driver.
Fig. 6,7 and 8 are the sequence diagrams for the operation for showing various aspects of the invention.
Fig. 9 is the slip buffer for adjusting the delay phase of output waveform.
Figure 10,11 and 12 show different broadcast system topologies.
Figure 13 is the sequence diagram for showing simplified analog- and digital- alignment timing.
Figure 14 and 15 is exporter sequence diagram synchronous and asynchronous starting with exciter engine.
Specific embodiment
On the one hand, the present invention relates to the single frequency networks supported for holding in in-band channel (IBOC) system
(SFN) or booster apply required time alignment method and apparatus.On the other hand, the present invention relates to for adjust by
The method and apparatus of the delay phase of the waveform of multiple transmitters output in SFN.
Fig. 1 shows broadcast system 10, wherein, it is transmitted simultaneously from studio to two emitter positions by STL same
A audio program.In this example, using the link (STL) 18 and 20 between studio and transmitter, to two remote transmitters
The programme content that 14 and 16 (being known respectively as station 1 and 2) transmission originate at first transmitter (for example, studio) 12.Pass through
Ellipse 22 shows 1 overlay area of station.2 overlay areas of station are shown by ellipse 24.Two emitter positions have phase
Deng transmission power.When receiver is located at 1 overlay area of station, the signal strength from station 2 is sufficiently low, is connect not interfere with
It receives.When receiver is located at 2 overlay area of station, opposite situation is generated.Overlay area be generally defined as 20dB it is desired/
Undesirable (D/U) profile.
However, when receiver is located at overlay region 26, it is received from two emitter positions, and there is power ratio to be less than 20dB
Signal.In these cases, if the delay between two signals is less than guard time or 75 μ sec, receiver is substantially
It under multi-path condition, can most possibly negotiate this condition, and continue to HD radio signals, particularly under steam
In automobile.However, when relative delay becomes larger than 75 μ sec, intersymbol interference (ISI) can be generated, and be contemplated that and receive
Device will not be able to be decoded HD radio signals, and will be returned to and only receive simulation.
In the case that point in phase equifield intensity is not located at equidistance point and requires reception, it can use described herein
Slip buffer technology come intentionally and accurately change the signal delay in one of transmitter.This can change signal delay song
Line relative to signal level curve position, in this way, problematic region can be eliminated or allow them to be transferred to such as mountain
The area that no one above top or water body etc lives.
Fig. 2 shows the basic schematic diagrames of IBOC SFN.In this figure, first transmitter (for example, studio) and long-range
STL 30 between transmitter can be microwave, Tl, satellite, cable etc..In fig. 2, studio 10 is shown as including audio
Source 32, synchronizer 34 and STL transmitters 36.Synchronizer 34 is received from by the global positioning system (GPS) shown in GPS antenna 38
Timing signal.Timing signal from global positioning system serves as master clock signal.Transmitter is also referred to as platform.
It stands and 12 is shown as including STL receivers 40, synchronizer 42, driver 44 and antenna 46.Synchronizer 42 is from passing through
Global positioning system (GPS) shown in GPS antenna 48 receives timing signal.
It stands and 14 is shown as including STL receivers 50, synchronizer 52, driver 54 and antenna 56.Synchronizer 52 is from passing through
Global positioning system (GPS) shown in GPS antenna 58 receives timing signal.Timing signal from global positioning system serves as master
Clock signal.
Fig. 3 is can be used to play the studio position 60 of FM IBOC signals, FM emitter positions 62 and perform in a radio or TV programme
The functional block diagram of the associated component of room transmitter link (STL) 64.Studio position includes, wherein, studio automation equipment
84th, inducting device 68, exporter 70, driver ancillary service unit (EASU) 72 and STL transmitters 98.Emitter position packet
Include STL receivers 104, the digit driver 106 including exciter engine subsystem 108 and analog driver 110.
At the position of studio, studio automation equipment provides star turn service (MPS) audio 92, guide to EASU
Go out device and MPS data 90 is provided, program service (SPS) audio 88 of supplement is provided to inducting device, and SPS data is provided to inducting device
86.MPS audio serves as main audio program source.In a hybrid mode, it remains the existing mould in analog- and digital- transmission
Intend radio programming formats.Also referred to as the MPS data of program service data (PSD) includes such as music title, singer, album name
The information of title etc..The program service of supplement may include the audio content and relevant with program for the service of supplement
Data.
Inducting device includes the hardware and software for providing advanced application service (AAS)." service " is broadcasted via IBOC
Signal sends the content of user to, and may include being not classified as any kind of data of MPS or SPS.The example of AAS data
Attached bag includes real-time traffic and Weather information, navigation picture update or other images, electronic program guides, multicast program, multimedia section
Mesh, other audio services and other contents.The content of AAS can be provided by service provider 94, and service provider 94 is to importing
Device provides service data 96.Service provider can be derived from positioned at the broadcaster of studio position or service and content
External third party provider.Inducting device can establish session connection between multiple service providers.Inducting device is encoded and is answered
With service data 86, SPS audios 88 and SPS data 96 to generate exporter link data 74, the data 74 are again via data
Link is output to exporter.
Exporter 70 is included as providing for needed for the star turn service (MPS) of broadcasting and station information service (SIS)
Hardware and software.SIS provides such as catchword, absolute time, the station information with the relevant positions of GPS etc..Exporter
Digital MPS audio 76 is received, and compress audio by audio interface.Exporter is also multiplexed MPS data 80, exporter link data
74 and the digital MPS audio through overcompression, to generate exciter link data 82.In addition, exporter is also connect by its audio
Mouth receives simulation MPS audio 78 and the delay of preprogramming is applied to it, to generate the simulation MPS audio signal 90 postponed.This
Analogue audio frequency can be played as mixing the spare channel of IBOC broadcast.The system of delay compensation digital MPS audio is prolonged
Late so that receiver can be allocated between number and analog program, be deviated without generation time.In AM Transmission systems,
The MPS audio signal 90 of delay is converted into mono signal, and the part as exciter link data 102 is directly by exporter
The link (STL) being sent between studio and transmitter.
EASU 72 receives MPS audio 92 from studio automation equipment, it is converted to appropriate system in terms of rate
Clock, and two copies of output signal, one is the 76 of number, and one is the 78 of simulation.EASU includes being connected to antenna 75
GPS receiver.GPS receiver enables EASU to obtain master clock signal, the master clock signal be synchronized with driver when
Clock.EASU provides main system clock used in exporter.EASU is additionally operable to simultaneously can not in the catastrophic failure of exporter generation
Simulation MPS audio is bypassed into (or redirection) in the case of reruning, is not passed through exporter.The audio 82 bypassed can be direct
STL transmitters are fed to, eliminate dead-air event.
STL transmitters 98 receive the simulation MPS audio 100 of delay and exciter link data 102.It passes through STL link
64 output driver link datas and the simulation MPS audio of delay, link 64 can be unidirectional or two-way.STL link
It can be such as digital microwave or ethernet link, and Standard User datagram protocol (UDP) or standard transmission control can be used
Agreement (TCP) processed.
Emitter position includes STL receivers 104, driver 106 and analog driver 110.STL receivers 104 are logical
It crosses STL link 64 and receives the exciter link data for including audio and data-signal and order and control message.By driver
Link data is transmitted to the driver 106 for generating IBOC waveform.Driver includes host-processor, digital up-converter, RF
Up-converter and exciter engine subsystem 108.Exciter engine receives exciter link data, and modulates IBOC
The numerical portion of DAB waveform.The digital up-converter of driver 106 becomes the baseband portion that exciter engine exports from number
It is changed to simulation.Steering D/A conversion is carried out based on GPS clock, GPS clock and exporter it is based on GPS, obtained from EASU
Clock is shared.In this way, driver 106 further includes GPS unit and antenna 107.
Analog signal is transformed to appropriate in-band channel frequency by the RF up-converters of driver upwards.It then, will be through
It crosses to the signal of up conversion and is passed to high power amplifier 112 and antenna 114, for broadcasting.In AM Transmission systems, swash
Device engine subsystem is encouraged consistently backup simulation MPS audio is added in digital waveform in composite mode；In this way, AM is transmitted
System does not include analog driver 110.In addition, driver 106 also generates phase and amplitude information, and digital and analogue signals are directly defeated
Go out to high power amplifier.
In certain configurations, the function of monolithic exciter combination exporter and exciter engine, such as the broadcast system of Figure 10
Shown in topology.In this case, driver 108' includes the hardware and software provided needed for MPS and SIS.SIS and EASU
GPS unit connection in 72', to obtain transmission timing and location information required information.Driver 108' is connect by its audio
Mouth receives the digital MPS audio from audio processor 210, and compresses the audio.Then, this audio through overcompression with it is online
The star turn service data (PSD) and advanced application service data flow that driver is fed on road 212 are re-used.Then,
Driver performs OFDM modulation to the bit stream that this is multiplexed, to form the numerical portion of HD radio waveforms.Driver also passes through it
Audio interface receives simulation MPS audio, and the delay of application preprogramming from audio processor 214.This audio is matched as mixing
Spare channel in putting plays.Digital display circuit delay in delay compensation digital MPS audio so that receiver can be in number
It mixes between analog program, is deviated without generation time.The simulation MPS audio of delay is sent to STL or directly transmits
To analog driver 110.
The component of broadcast system can be disposed in two basic topologies, as shown in FIG. 10 and 11.In single frequency network
In context, studio position can be considered as to source, and transmitting position can be considered as node.Do not increasing STL chains significantly
In the case that the bandwidth on road is to adapt to additional HD multiple radio audio channels, monolithic topology illustrated in fig. 10 cannot support AAS
Service.However, 70/ exciter engine of exporter, 109 topology illustrated in fig. 11 supports addition AAS services naturally, because of AAS
Audio/data is handled first, and is multiplexed to existing E2X chains road, without STL bandwidth requirements extraly are increased to height
Required bandwidth requirement is serviced in MPS.This topology is illustrated in greater detail in fig. 12.
Project comparable each other in Fig. 3,10,11 and 12 has identical items number.
Using various waveforms, IBOC signals can be emitted in AM and FM radio bands.Waveform includes FM mixing IBOC
The digital IBOC DAB waveforms of DAB waveform, FM, AM mixing IBOC DAB waveforms and the digital IBOC DAB waveforms of AM.
Fig. 4 show can be used to implement the present invention exporter system 120 and exciter engine system 122 it is certain
Partial fundamental block diagram is shown with the configuration for emphasizing the clock signal in whole system.Exporter system is shown as including to be embedded in
Formula exporter 124, exporter host 126, phase-locked loop (PLL) 128 and GPS receiver 130.132 receiving circuit of audio card
Analogue audio frequency on 134, and analogue audio frequency is sent to the exporter host in bus 136.Exporter host is by the mould of delay
Intend audio and be sent back to audio card 132.The analogue audio frequency of delay is sent to the analog driver on circuit 138 by audio card 132.
Digital audio in 140 receiving circuit 142 of audio card, and digital audio is sent to the exporter in bus 144
Host.The digital audio of decompression is sent back to audio card 140 by exporter host.Digital audio can be monitored on circuit 146.
AAS data is supplied to exporter host on circuit 148.GPS receiver is coupled to GPS antenna 150, to connect
Receive GPS signal.GPS receiver generates the clock signal of a pulse (1-PPS) per second on circuit 152, and on circuit 154
Generate 10MHz signals.44.1 clock signals are supplied to audio card by PLL.Exporter host on circuit 156 by exporter to swash
It encourages device engine (E2X) data and is sent to exciter engine.
Exciter engine system be shown as including embedded exciter engine 158, exciter engine host 160, number to
Upconverter (DUC) 162, RF up-converters (RUC) 164 and GPS receiver 168.GPS receiver is coupled to GPS days
Line 170, to receive GPS signal.GPS receiver generates the clock signal of a pulse (1-PPS) per second on circuit 172.
In general, driver be substantially exporter and exciter engine in single chest, combination have exporter master
Machine and exciter engine host function.Equally, in one implementation, GPS unit and various PLL may reside in EASU.
However, in Fig. 4, for simplicity, they are illustrated as residing in exporter and exciter engine.
From fig. 4, it can be seen that DUC and audio card are all driven by identical 10MHz clocks, if both of which
GPS is synchronized to GPS 1-PPS signals.Both exporter host and exciter engine host can access a pulse per second
The clock signal of (1-PPS).This clock signal is used to audio sample and waveform is supplied to start the accurate trigger that starts
The two.In exporter host, 1-PPS clock signals be used to generate with station information service (SIS) data together with transmit when
Between signal (ALFN).This system is relative delay between analogue audio frequency and digital audio on one side.
Figure 13 shows the schematic diagram of this timing.In t0, audio card starts to collect both analog- and digital- audio samples.For
Digital channel, these samples can be in t at themdIt is buffered and is compressed first by processing and wirelessly before transmission.It is slow
It is exactly 1 modem frame or~1.4861 seconds to rush section length, and it is about 0.55 second to handle delay.Once receive number
Word signal, receiver will just spend 3 modem frames (or~4.4582 seconds) to handle digital signal, and make digital audio
In tfIt can use.Therefore, in order to make analog and digital signal by time alignment, in tf, analogue audio frequency must be delayed by 4 modulatedemodulates
Adjust device frame that can be just transmitted after adding any driver processing delay (~6.5 seconds).Any analogue audio frequency processing delay is propagated
Delay is not all expressed, because they are too small, it is difficult to it is expressed, but when the multiple transmitting positions of trial synchronous averaging, it can
It can need to consider.
From the point of view of software respective, such as cited NRSC-5 files are described herein before, according to logical protocol storehouse,
Perform the encapsulation and modulation of HD radio broadcast contents.This multi-thread environment, when for needing pin-point accuracy and repeatable open
When in the system of dynamic timing, tool is there are one major defect, because specifying time segment to each thread, and operating system is assisted
When the scheduling that reconciles carries out particular thread, leads to the inherent variability of receiving thread processing data.This is most to close in layer 1 (modulating layer)
Key, wherein, DUC is not activated, until until it has handled the first data frame.As a result, start to receive when audio card
Collect sample when and when DUC start export sample when between there are intrinsic shakes.When being restarted system, this shake is originally
Body shows as analog/digital misalignment.Observe that startup shake almost has 20msec.Execution level 4 is embedding to the function in layer 1
Entering formula exporter improves original multi-threading, the timing of whole system is reduced into more deterministic：It is present to start shake
In about 1msec.Although starting shake to be substantially shrunk, if beginning and DUC waveforms without audio sample
Beginning between certain type of synchronization, then it be never eliminated.System described herein for SFN designs solution
It has determined this intrinsic startup timing mutability.
Based on system requirements, there are four main aspects for this design：Waveform accuracy, time alignment, frequency alignment, Yi Jike
Modulability.Each aspect in these aspects is solved successively.
Waveform accuracy
About waveform accuracy, because the time domain waveform broadcasted by each transmitter must be it is identical, each
OFDM symbol cannot be time alignment, but must include identical information.Each transmitter in SFN must be
Same time radiates identical OFDM symbol so that data are synchronous in the time domain.The accuracy of OFDM symbol is it is meant that must
Information (both audio and data) must be handled in an identical manner.That is, for the tiered system architecture in HD radio systems
In, each 1 protocol Data Unit of layer (PDU) modulated must be that position is accurate.
Although monolithic topology illustrated in fig. 10 is for existing SFN is enabled gradually to move to HD radio broadcastings
Advantageous, it is unpractical from the viewpoint of waveform accuracy still.First, audio codec display lag, and
In the case where not checking the history of input, unpredictable output.If it means that a node of network with other sections
The point different time is activated, then the output from audio codec can be different, even if the audio letter of input system
It number is aligned completely.Secondly, the PSD information of input system is non-deterministic, and also show lag.Finally, monolithic
Topology will not easily allow to use Premium Features.
The shortcomings that given above monolithic topology, for supporting that the selection of the logic of SFN is leading shown by Figure 11 and 12
Go out device/exciter engine topology.In this topology, from single point processing for institute's active material of each network node, production
The raw accurate layer 1PDU in position, because layer 1 handles (that is, display does not lag) of being to determine property, in the case where giving identical input,
Each exciter engine node will generate identical waveform.
Exporter/exciter engine topology is not limited to single exporter exciter engine pair, but exporter software quilt
It is designed to send identical data to multiple exciter engines.It has to be taken care that ensure the number of supported exciter engine (node)
Measure the timing restriction without departing from system.If the quantity of node becomes more, udp broadcast or multicast capability must be added to extensively
In broadcast system.
Time alignment
About time alignment, it is necessary to generate identical OFDM waveforms at each node of SFN, each in SFN
Node must assure that it just while transmit identical OFDM symbol.As used in this description, node refers to drill
Broadcast room STL transmitters and distant station transmitter.
Both synchronous averaging and asynchronous starting must be solved.Synchronous averaging is the exciter engine at each node
It is online and before exporter is reached the standard grade etc. data to be received.Asynchronous starting is in any random time list after exporter is online
The situation that exciter engine at a node is reached the standard grade.In both cases, it is necessary to assure OFDM waveforms at all nodes
Absolute time is aligned.In addition, any method of time alignment all must be strong for network jitter, and solve each net
The different network path delays of network node.
During known SFN is realized before most of, the certain extra datas for being sent to each node are added to STL
In link.This other data is substantially timing reference signal.At each node, OFDM modulators are stabbed using this time
Local delay is calculated, to realize public wireless broadcast time.However, the method for the present invention is believed using 1-PPS GPS clocks
Certain relationships or geometric data (geometry) number between the ALFN times associated with each data frame are exhausted to ensure
To time alignment, additional timing information is sent without across E2X link.
SFN requirements, if actuator position each other and with it is main and be the asynchronous wire over ground of unique exporter, protect
The absolute time between position is stayed to be aligned.It is (actuator position is online before exporter is reached the standard grade) and asynchronous in this way, synchronous averaging
Start the two to be required for retaining waveform alignment.That is, each driver on network will be identical with each other driver
Moment generates same waveform.
Method as described herein is effective in each position for needing to be aligned dependent on GPS receiver, and
It is locked out.GPS receiver provides a pulse (1-PPS) hardware signal per second, and the signal is by cross-platform ground generation time pair
Standard, and the 10MHz signals from GPS by cross-platform generate frequency and phase alignment.Waveform will be in absolute 1 frame number of layer
(ALFN) it is aligned and starts, ALFN is that a rational (44100/65536) is multiplied by since on January 6 1980 GPS time started
Noon 12:The index of number of seconds since 00.Star turn service (MPS) audio in exporter is initially controlled so that
Waveform can start in ALFN time boundaries, with synchronous averaging (exciter engine has been reached the standard grade and waited for) or asynchronous open
Dynamic (any random time exciter engine after exporter is effective is online).
Can be used to ensure that digital waveform the mechanism that accurate ALFN time boundaries start be will number upwards
Frequency converter (DUC) is placed in one can provide the operation mode of offset to DUC.When offset control DUC waveforms will be in next 1-
Start after PPS signal, next 1-PPS signals are entered on interrupt line.1-PPS signals are input into DUC, as right
Control the interruption of the firmware handle device of DUC.In DUC driver levels, provide to DUC firmware handles device " will next 1-PPS it
The millimicro number of seconds started afterwards " value, the value have about 17 nanoseconds of resolution ratio.Time quantum is transformed to DUC firmware handle devices
The 59.535MHz clock cycle quantity.For startup such DUC " arm-to-arm " or setting will so that for
" hardware level " time of DUC waveforms being capable of synchronous averaging.
The correct time for knowing the first audio sample be it is highly important, so as to make the audio time started to waveform start when
Between keep constant.Certain audio cards can by by DUC hardware awaited orders interruption and triggering it is similar in a manner of come await orders interrupt and
Triggering.An example for not having the audio card of hardware trigger is iBiquity reference audio cards.Instead of hardware trigger, audio card
Driver obtains 64 cycle counts of host-processor when audio card is activated.When inputting 1-PPS signals, master is also obtained
The cycle count of machine processor, in this way, in the presence of the time mechanism associated with GPS time that audio is started to sampling.Preferred
Method can directly be associated with audio sample with 1-PPS signals.
As long as the first few hundred millisecond of one of the audio card in 3 potential 1-PPS signals is activated, then, there will be
One geometric data so that when receiving data-message at exciter engine, unique list will be had before next ALFN
One 1-PPS signals have enough time to utilize and the necessary delays of next ALFN are buffered, DUC is interrupted to await orders.Show in fig. 14
The example of this synchronization " bootable " geometric data is gone out.In the case of asynchronous starting, logical framing is had been set up.But
Be because there is no integer relation between ALFN and 1-PPS signals, and the startup time of exporter be it is unknown, therefore, 1-
Phase between PPS and correct ALFN is also unknown.As long as the audio card in exporter is before appropriate 1-PPS signals
It is activated within~0.9 second, it is possible to establish a geometric data so that instant ALFN or next ALFN, which will be shown, starts DUC institutes
The appropriate 1-PPS needed and ALFN relationships.The example of this situation is shown in FIG. 15.
Fig. 5 is for verifying the fractionation configuration exporter platform 180 of cross-platform synchronization and the frame of exciter engine platform 182
Figure.From fig. 5, it can be seen that exporter and exciter engine platform respectively have GPS receiver 184,186, they are all cited
To common time base (that is, master clock).In exporter platform, the 1-PPS pulses as caused by GPS receiver unit are directed to
Parallel port pin 188, and it is input into exporter host code.It should be understood that show can be with many sides for the block diagram of Fig. 5
The function set that formula is realized.
One preferred realization uses the space-time management for being referred to as TSMX on exporter platform and exciter engine platform
Software module.The role of TSMX modules in synchronous averaging application is the GPS for collecting 64 cycle counts with 1-PPS signals
Temporal information, and audio layer (on exporter platform) or exciter engine II category codes is supplied to (to swash all information
It encourages on device engine platform).When inputting 1-PPS signals on parallel port, TSMX modules 190 will come from via serial port
The timestamp of GPS hardware is accurately attached to 64 cycle counts.Necessary information can be supplied to audio layer 192 by this, so as to
It can attempt synchronous averaging.Audio-frequency information from audio layer is passed into embedded exporter 194, and pass through data link and answer
Exciter engine is transferred to device 196.
On exciter engine platform, DUC hardware 198 is included as hardware level interrupt signal, and 1- is inputted from GPS receiver
The mechanism of PPS hardware signals.In input terminal, this information is covered timestamp (64 cycle counts), and is sent to TSMX moulds
Block 200.GPS time together with the 64 bit cyclic count packs of the last one 1-PPS, is made them to excitation by TSMX modules
Device engine II category codes can be used, at the beginning of calculating suitably.Using this mechanism, exporter platform and exciter engine platform
Both substantially on common time base.The timing relationship between 1-PPS clock signals and ALFN timings is described below.
Potential ALFN times (correct time, every 1.486077 seconds) and 1-PPS times are completely asynchronous.In this way, it is
Processing any arbitrary system time started, synchronous averaging algorithm must handle any possible 1-PPS and ALFN time geometries
Data.
It can be shown that if the first few hundred millisecond of one of the audio card in 3 potential 1-PPS signals is activated, that
There will be a timing geometric datas so that, will before next ALFN when receiving data-message at exciter engine
Unique single 1-PPS signals are had, have enough time to await orders interruption or setting DUC to start in next ALFN times.
In order to ensure " bootable " geometric data of 1-PPS and ALFN times, a theorem, the theorem have been developed
Limit the distance between ALFN times and any 3 continuous 1-PPS for synchronous averaging.ALFN times, 1-PPS and sound
" bootable " geometric data that frequency starts audio occurs first is started to sample in the first few hundred millisecond of next 1-PPS.At this
On 1-PPS, using the necessary delay after the 1-PPS come await orders interrupt DUC, to start waveform so that waveform under surely
True ALFN time transition is logical.
If waveform starts in the ALFN times, then the ALFN times must be more than a certain numerical value after the 1-PPS so that
It can await orders and interrupt DUC.
The ALFN times can be expressed as：
am=(α/β) m
Wherein, 2 β and m of β ＜ α ＜ are the ALFN indexes for being often referred to simply as ALFN.Under our specific condition, α=
65536, also, β=44100.For each n, there are three continuous integers, n, n+1, n+2 so that p ∈ (n, n+1, n+
2 } and
am- p ＜ 2- (α/β)
This is implied, there are geometric data in 3 1-PPS of any arbitrary system time started, regardless of arbitrary AFLN
Time/1-PPS geometric datas, wherein, the difference between ALFN times and 1-PPS is less than~0.5139 second.This makes it possible to set
Geometric data, wherein, audio starts to occur before 1-PPS, and the ALFN times occur after 1-PPS in 0.5139 second.
From the point of view of system perspective, this is important because exporter is by computational geometry data, and will 1-PPS it
Not long ago start audio sample, wherein, the ALFN times are in 0.5139 second.This will make audio start to start to keep to the greatest extent may be used to waveform
Can be small, and audio is still kept to start/1-PPS/ALFN time geometry data simultaneously.In a particular system, audio start to
Waveform is initially 0.9 second.
Fig. 6 is the timeline of exporter and the primary clustering in the operation of driver synchronous averaging.As shown in fig. 6, exporter
To wait for 1-PPS, and by this be called setting 1-PPS.At this point, L5 exporters code does not know 1-PPS the and ALFN times
Timing relationship.If next ALFN times are fallen in the region for being marked as " region for using pps n ", audio will be next
It is started within 0.9 second before 1-PPS.If next ALFN times are in the adjacent area labeled as the region of " using pps n+2 "
Occur, then audio starts to be delayed by, until being marked as in the row for being labeled as " audio sample starts " " uses pps n+
The region in 2 region ".The reason of this startup scheme will be delayed by is to start that 1- occurs between the ALFN times in audio
PPS, to start waveform.If not in 2 regions of this head, unique other possible places that the ALFN times may occur are located at mark
It is denoted as the region in " region for using pps n+1 ".If start scheme using this, then, audio starts will be labeled as " use
The region of pps n+1 " region occurs.
0.9 second period is selected, to meet synchronous averaging and asynchronous starting condition.Asynchronous condition be related to effective exporter with
And the exciter engine hereafter reached the standard grade.In the case, logical framing is established via exporter, however, in exciter engine
Start the time, we do not know the phase relation of 1-PPS and ALFN times.
In the case of asynchronous starting, logical framing is had been set up.It is but because not whole between ALFN and 1-PPS
Number relationship, and the startup time of exporter is unknown, and therefore, the phase between 1-PPS and correct ALFN times is also
Unknown.As long as it can be shown that the audio card in exporter before appropriate 1-PPS signals~be activated within 0.9 second, it is possible to
Establish a geometric data so that instant ALFN times or next ALFN times will show the appropriate 1- started needed for DUC
PPS and ALFN time relationships.
Fig. 7 is the timeline of exporter and the primary clustering in the operation of driver asynchronous starting.In the figure 7, on top, row shows
Go out through the ALFN indexes of ALFN time-divisions (m, m+1, m+2 ...), exporter timing is below, exciter engine timing
Below exporter timing.Bottom row shows the region of the support for corresponding ALFN (m, m+1 or m+2).Black square sub-line
And it is intended to show that possible many geometric datas between ALFN times and 1-PPS signals labeled as the frame of " 1 second ".It is important that
If it would be recognized that exporter as exporter row is described configured initial timing (0.9 second before the ALFN times
Start audio), then, no matter when online exciter engine is, they should all be received for about 0.7 second before the ALFN times
For the data of next ALFN time waveforms output.Then, according to bottom row, if next 1-PPS is happened at labeled as " PPS exists
Here, using the region of next ALFN ", then next ALFN times will be the waveform time started.If situation is not such, that
, it may be necessary to a modem frame (just 1 ALFN time) is skipped, and expects next ALFN times, to start wave
Shape.If all 1-PPS lines moved together, it is observed that being used to start the 1-PPS of waveform in the specific ALFN times
The region of support.
Fig. 7 shows needs 0.9 second to establish a geometric data so that when asynchronous starting occurs, can use i.e.
When ALFN (m) times or next ALFN (m+1) times be used as the waveform time started.A kind of specific implementation in frame of reference
It will be about spending 200 milliseconds clock information is begun to transfer to exciter engine from audio.
Check that the another way of the constraint of problem is as follows.If it is desirable that is found before the candidate ALFN times sharp
Encourage the satisfactory arm-to-arm time of device engine, then, in the point for meeting following equation
am-pn=arm- ε,
(wherein, arm is in next pn1-PPS and ALFN time anThe arm-to-arm time difference, ε is between guard time
Every), difference is too small and we must use next ALFN times.Managing the equation on the boundary will be
am+1-pn+2≥ε
It is substituted into from above equation, it has been found that
arm≥2-(α/β)
If we move the sequence of dark 1-PPS lines so that in the sword behind in first " 1 second " region there are one,
am-pn≤ε
So
am+1-pn+1=δ
But following equalities are also set up
am+1-pn+1≤arm-ε
δ is solved, we obtain
δ≥(α/β)-1+ε.
In this way, arm is selected to be divided into 25 milliseconds between the guard time of 0.7, ε, audio will be started to start to be set to waveform
About 0.9, and enough spaces are provided to support that the first ALFN times started or the 2nd ALFN times started.
Can be based on arm values, 1-PPS and when it is clear that be calculated we be in when, that is,
After clock signal has arrived at exciter engine, the ALFN times that can be used for starting waveform are simply calculated.However, checking
Each geometric data and depending on arm values have it is how small after, occur start geometric data before, future can be multiple ALFN
Time.
Fig. 8 show exporter it is synchronous with driver in primary clustering timeline.Here, it moves by unanimous on the whole
Dynamic 1-PPS lines, it can be seen that if we select too small audio to start to waveform time started interval, it may not be possible to find
There is the solution of the bootable geometric data of 1-PPS and ALFN times.For example as described herein, 0.9 or 0.8 second
Audio start to the waveform time started the bootable geometric data being enough to ensure that in multiple ALFN times.
The present invention provides the synchronous method for not requiring the transmission timing information together with the data of transmission.Described method
It is a kind of realize the certain features that may rely in hardware component, to ensure that accurate timing can be calculated.First, audio card
Or must have will allow they be activated on 1-PPS signals or the hardware trigger of delay start or replace rock noise
Frequency card must record cycle count when they start sampling, be calculated in this way, accurately timing can be performed.Although it can use
The audio card of cycle count is recorded, still, hardware trigger is much strong method.
Frequency alignment
For the networked system of the transmission facilities with GPS lock, total absolute number carrier frequency error must ±
It is 1.3Hz interior.For the system of the transmission facilities with non-GPS lock, total absolute number carrier frequency error must ±
In 130Hz.
Controllability
SFN requires to adjust the ability of waveform timing at each driver, to introduce the phase delay between each position.
These phase delays can be used to adjust for accurate overlay area profile.
Once the synchronous waveform between completing emitter position, it is possible to using the phase adjusted at each position,
To form the profile of overlapping coverage areas.In the case where unequal transmitter power balances, it is not located in the point of phase equifield intensity
In the case of equidistance point, the signal delay at one of transmitter must be changed intentionally and accurately.This can change
Delay curve eliminates problematic region or allows them to be transferred to such as mountain relative to the position of signal level curve
The area that no one above top or water body etc lives.
In order to promote " tuning " to SFN, slip buffer (such as Fig. 9 is added in warp-wise exciter engine software
It is shown) so that delay can be adjusted to the resolution ratio of 1FM samples or 1.344 μ sec or 1/4 mile of propagation delay and height
± 23.22 milliseconds or about ± 4300 miles of propagation delay compensated up to total delay.
Slip buffer is circular buffer, and length is 48 FM symbols.Since buffer write-in is accorded with one at a time
Number or 2160 IQ samples pair, each operation after, write-in pointer can be with incremental sign size, mould buffer size.Entirely
Buffer is that 48 symbols are long, and be written pointer will always character boundary enter a new line.
Buffer reading must be managed, is slided with allowing up to 1/4 FM blocks or the sample of 17280 IQ samples pair, forward direction
Or it is reversed.The control of slip buffer is only occurred in FM block boundaries, that is, per 32FM symbols or 92.88 milliseconds.Each
At a BOB(beginning of block), reading pointer advances or postpones the quantity of sample slip applied to the block, and then, entire data block is read
Into output buffer.It skips or repeated sample, to realize desired slip.By control interface, provide what is slided
Sample size and the quantity that the block slided should be applied to.Since reading pointer is initially 17280 behind write-in pointer
A sample and 17280 samples before the end of the first data block, before " slip " part of buffer is finished, it can
With either direction add up up to 17280 IQ samples slide.Due to arbitrary by movement in each block boundary reading pointer
The sample of quantity, therefore into fragment can be replicated to output buffer.Output buffer is had been duplicated into data
Later, after the last one is returned in output buffer, reading pointer will be directed toward IQ samples pair always.
It is obvious to those skilled in the art although describing the present invention according to multiple examples
It is that in the case of without departing from defined the scope of the present invention as the following claims, disclosed example can be made
Go out various changes.Implementations described above and other realizations are all in the range of claims.
Claims (8)
1. a kind of broadcasting method, including：
Include the signals of the multiple data frames synchronous with the first GPS pulse signal using first transmitter to send；
The signal is received at the first remote transmitter；
Make the frame synchronization at first remote transmitter in the second GPS pulse signal；
By synchronization frame from the remote transmitter be transferred to multiple receivers and
Audio-frequency information is sampled and sample is combined as the multiple data frame, wherein, exist for the sampling of each frame
Start in the predetermined time of a pulse in the first GPS pulse signal, and each frame and absolute 1 frame number phase of layer
Association.
2. the method for claim 1, wherein each frame is initially corresponding to absolute 1 frame number of layer
What the time was sent.
3. a kind of broadcast system, including：
First transmitter, for sending the signal for including the multiple data frames synchronous with the first GPS pulse signal；And
First remote transmitter, including being used for the frame is synchronous with the second GPS pulse signal and being used to arrive sync frame transmission
The circuit of multiple receivers, wherein the first transmitter sampled audio information and sample is combined as the multiple data frame,
Wherein, start in the predetermined time of a pulse for the sampling of each frame in the first GPS pulse signal, and
Each frame is associated with absolute 1 frame number of layer.
4. broadcast system as claimed in claim 3, wherein, each frame is initially to be compiled corresponding to absolute 1 frame of layer
Number time sent.
5. a kind of method that platform made in broadcast system synchronizes, the method includes：
Master clock signal is received at base transmitter and multiple remote transmitters；
Start in the predetermined time interval before the first clock pulses in the master clock signal in the Ji Fasheqichu
Audio sample；
Audio sample is combined as audio frame；
The 1 frame number time of absolute layer occurred after first clock pulses, start to send out the audio frame from the base
Emitter is transferred to the remote transmitter；
The audio frame is received at the remote transmitter；And
Since corresponding to the time of the audio frame at the absolute 1 frame number time of layer, the sound is transmitted from the remote transmitter
Frequency frame.
6. method as claimed in claim 5, wherein, the master clock signal includes the clock pulses with a pulse per second
GPS clock.
7. it method as claimed in claim 6, further includes：
Offset is supplied to digital up-converter, wherein, the offset is should to connect the number wherein to upconvert
Time quantum after next GPS clock pulse of device waveform.
8. method as claimed in claim 5, wherein, predetermined time interval is 0.9 second.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US12/346,955 US8279908B2 (en) | 2008-12-31 | 2008-12-31 | Synchronization of separated platforms in an HD radio broadcast single frequency network |
| US12/346,955 | 2008-12-31 | ||
| CN2009801532101A CN102272621B (en) | 2008-12-31 | 2009-12-03 | Synchronization of separated platforms in an hd radio broadcast single frequency network |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2009801532101A Division CN102272621B (en) | 2008-12-31 | 2009-12-03 | Synchronization of separated platforms in an hd radio broadcast single frequency network |
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| Publication Number | Publication Date |
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| CN105356959B true CN105356959B (en) | 2018-06-15 |
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| CN201510809403.5A Active CN105356959B (en) | 2008-12-31 | 2009-12-03 | The synchronization of the platform of separation in HD radio broadcasting single frequency networks |
| CN2009801532101A Active CN102272621B (en) | 2008-12-31 | 2009-12-03 | Synchronization of separated platforms in an hd radio broadcast single frequency network |
| CN201310426204.7A Active CN103475434B (en) | 2008-12-31 | 2009-12-03 | The platform of the separation in HD radio broadcasting single frequency network synchronous |
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| CN201310426204.7A Active CN103475434B (en) | 2008-12-31 | 2009-12-03 | The platform of the separation in HD radio broadcasting single frequency network synchronous |
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| CN (3) | CN105356959B (en) |
| BR (1) | BRPI0923905A2 (en) |
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| IT201800003405A1 (en) * | 2018-03-09 | 2019-09-09 | Abe Elettr Srl | ISOFREQUENCY TRANSMISSION-DIFFUSION SYSTEM AND FM ISOMODULATION WITH DIGITAL TECHNIQUE. |
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| US10944535B2 (en) * | 2019-05-29 | 2021-03-09 | Shure Acquisition Holdings, Inc. | OFDMA baseband clock synchronization |
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Also Published As
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| CN103475434B (en) | 2015-12-23 |
| BRPI0923905A2 (en) | 2019-09-03 |
| CN105356959A (en) | 2016-02-24 |
| US8279908B2 (en) | 2012-10-02 |
| MX2011006938A (en) | 2011-07-20 |
| CA2750157C (en) | 2017-03-28 |
| CN102272621A (en) | 2011-12-07 |
| CA3035925C (en) | 2021-07-27 |
| CN102272621B (en) | 2013-11-20 |
| CN103475434A (en) | 2013-12-25 |
| CA2895936A1 (en) | 2010-07-08 |
| CA2895936C (en) | 2019-04-02 |
| US20100166042A1 (en) | 2010-07-01 |
| CA3035925A1 (en) | 2010-07-08 |
| CA2750157A1 (en) | 2010-07-08 |
| WO2010077543A1 (en) | 2010-07-08 |
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